Our overall goal is to continue to produce new knowledge of the regulation of lung growth from fetal life through adolescence. In Project 1, Smith et al will pursue purification and synthesis of fibroblast pneumonocyte factor. The role of growth factors and hormones in alveolar cell maturation will be pursued. In Project 3, Taeusch and Phelps plan to evaluate the role of surfactant associated proteins. Further isolation, purification, and functional evaluation are underway. Surfactant replacement will be pursued, with reference to the best method of distribution, study of batch to batch variability of TA surfactant, and definition of lower age group that might be expected to respond. Work on lung mechanics will take new directions as Fredberg assumes leadership of the group studying the mechanism of high frequency ventilation and Frantz pursues an NIH sponsored clinical trial. Stark et al will investigate the role of the diaphragm and larynx in maintenance of lung volume in infants. Wohl, Castile et al will follow the infants who had combinations of preterm birth and lung injury with respect to later lung growth. Infants who received surfactant replacement in the 1984-85 study will be recruited into pulmonary and neurologic and immunologic follow up studies.